Polishing felt



Nov. 8, 1966 w. E. BECKER 3,283,451

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AT TORN EYS United States Patent O 3,283,451 POLISHING FELT William E. Becker, Norton, Mass., assigner to Bacon Felt Company, Taunton, Mass., a corporation of Massachusetts p p Filed May 13, 1964, Ser. No. 366,955 16 Claims. (Cl. 51-380) This invention relates to a specially designed, mechanically attached felt polishing unit of the type used in .the polishing of plate glass, stone, or other large plane surfaces.

Continuous ribbons of large plate surfaces, such as lglass, are commonly polished by means of a plurality of slurry-saturated felts moving rapidly against and over the surfaces thereof. Usually the felt is arranged in clusters mounted around a power-driven spindle, which causes the at felt surface to follow .a circular path. The geometry of the felt when in operation is effectively circular, which permits for a smooth uniform turning of the individual polishing felts.

The securing ofthe -felt surface lto .the base of the metal polishing block has been `accomplished by either of two methods. The rst `and more traditional system has been one of mechanically holding the felt in place by causing the Y:outer periphery of the felt to bend laround the outer periphery of the polishing block and to :he held in place by an outer ring. The outer ring is secured in place by the tightness of iit and the 4resiliency of the felt held between the ring and the metal fblock.

Because of the physical properties of conventional polishing felt, it has been found impractical to :bend felt whose thickness exceeds 1% inches, Ithus limiting the use of felt to approximately this thickness. For reasons of useful life, economy of slurry, uniformity of operation, and .less -down time, it would be advantageous to use thicker felt.

Another difficulty with the `locking ring device described above maybe found in the method used to press the ring in place. Due to the Weight and bulk :of the metal polishin'g block it is necessary to use special handling equipment, such as lifts, jacks and hydraulic presses adapted to this Q purpose. Also lack of ring pressure, uniformity and alignment at .the press-on operation can cause 4inconsistencies in the free turning of the felt in operation and, therefore, premature wear and poor polishing quality.

The second well known method of felt attachment .to the polishing block is accomplished lthrough the use of adhesives. Solvent release and hot melt types have been used, however, their success is predicated on many variables. Some of these variables -are toghe found in the chemical make-up of the `adhesive itself, such `as pot life volatility, flow temperature and degree of cure, while others are to be found in the physical nature of the bonding surfaces. One of the first prerequisites of a secure bond is to be found in .the condition of the bonding surfaces, which requires that traces of previous adhesives as well as polishing line contaminates be removed from the polishing block and that the felt bonding -surface be sized or conditioned with cement. Obviously this step is timeconsuming and requires physical removal of the polishing block from ythe polishing area.

There are obvious safety hazards involved with use of large volumes of cements and adhesives, such Kas fumes,

i tures described in my U.S. Patent 3,169,265 of February 16, 1965 and entitled Composite Resilient Polishing Pad and Method for Making Same in a polishing felt ICC ' i whose vgeometry is hat, similar to the adhesively attached.l However, with the mechanically felt described above. held felt described in this invention it is now simple and practical to incorpo-rate a resilient member under the critical center portion of the hat polishing felts.

Still another diiliculty with an adhesively held polishing felt is to be found in the inherent lack of uniform penetration of the preconditioning cement, or hot melt cement, applied to the back of the pad. As the felt Wears to approximately 1/2 inch remaining thickness, hard spots in the felt face are encountered. These hand .areas are traceable to the uneven penetration of the preconditioning cement and are the cause for lthe pre-mature removal of the felt from operation.

With the demand for continually high line speeds resulting in increased pressures, shear forces and operating temperatures, it is evident that a more positive method of attaching felt to the polishing block is required.

The principal object of this invention is to provide a combination polishing block and unitary polishing felt in which the block is provided with a cavity in the outer face, the felt is provided with an opstanding boss seated in the cavity and laterally extending means in the plane of the boss and cavity to retain the felt on the block.

Another object of the invention is to provide a more secure, Iless costly .and :less dangerous system for attach- :ing and replacing polishing felts, the system being mechanical but not requiring clamping pressures .and being free from safety and operational hazards.

A further object of the invention is to provide an improved, unitary polishing felt having an upstanding, inverted, truncated-conical, anchoring portion htting in a mating, split ring detachably fixed to the outer .face of a polishing block, attachment and replacement of the felt requiring -only the later-al removal of half the ring and sliding the -felt laterally on or off the block.

Still another object of .the invention is to provide an improved polishing felt with a laterally 4recessed attachment portion of soft, and preferably slightly resilient, material detachably mounted on a polishing |block by a ring on the face of Ithe polishing block which encircles the attachment portion, the entire Working surface of the felt being usable .and the inner central portion of the attachment portion being usable for 1cushioning means.

A still further object of the invention is to provide an improved polishing felt in which positive mechanical attachment to the block -does not require bending the felt around the block, whereby the felt may be of :increased thickness, operated at higher unit pressure, speed and temperatures, and gives improved economy of felt life, polishing slurry and down time for replacement.

Other -objects and advantages of the invention will be apparent )from the claims, the `description of the drawing and from the drawing in which: l .Y

FIGURE `1 is a side elevation, in half section of a preferred embodiment of the invention. n

FIGURE 2 is ya view similar to FIGURE l showing the split ring separated for slidablel insertion of `a felt.

FIGURE 3 is a view similar to FIGURE 1 showing an embodiment of the invention adapted for central feed of slurry, and Y FIGURE 4 is a view similar to FIGURE 1 showing an embodiment of the invention with tooth-like cushion means and slurry troughs In FIGURE 1 a typical polishing block 30 is shown, the block 30 4being rotatably mounted in a conventional plate glass polishing machine, to freely rotate over a moving sheet of plate glass 31 on the arms of a power driven spindle. The block 30 includes an outer', feltcontacting face 32 which is ilat and of circular periphery 33 in the conventional manner.

Patented Nov. 8, 1966 The unitary, composite polishing felt 34 of the inven- -.tion, is of predetermined thickness, preferably greater than the conventional one and one quarter inch thick ,s felts now much in use. Felt 34 may be of any desired f; known structure in the outer working portion 35 thereof,`

j portion 37,'may be about one half inch thick. The cylin-` dricalbody 38 of the outer working portion 35 is of predetermined diameter, preferably equal to the diameter of the block 30.

Laterally directed recess means 40 is provided in the exterior side wall of the anchoring portion 37, the means 40 extending inwardly toward the centre of the felt from the outside to receive anchoring elements. The anchoring portion 37 is integral with the working portion 35, of felt 34, and upstanding therefrom, the portion 37 preferably being of reduced diameter to form a centrally disposed projection, or boss, with an exterior side wall 41. I use the term boss in the sense of a projection above the general surface of the felt body to form a seat for another part, namely, a split ring. v

Preferably the anchoring portion, or boss, 37 is 0f invertedtruncated conical, configuration so that the side wall 41, forms an undercut, tapered groove 42 which converges from the block-engaging face 43toward the working face 36. Thus, in the preferred form of the invention the laterally directed recess means which extends inwardly toward the centre of the felt 34 is the annular, undercut tapered groove 42.

As shown in FIGURE l, the felt 45 of the working portion 35 is firmly adhered and united to a closely woven the anchoring portion 37 is filled with a soft resilient cushion material 49, such as foam rubber, or felt and the `entire anchoring portion 37 is enclosed in a covering layer 50 of impermeable cured rubber material, similar to material 47. The side wall 41 which forms the undercut groove 42, `and the laterally directed recess means 40, is thus shielded, sealed and strengthened by the rubber layer 50 and the layer 50 together with the rubber 47 firmly binds and adheresthe Vcanvas 48 and the filler 49 to the felt 45.

The composite polishing felt 34 is made by placing a sheet of serni-cured rubber on the felt 45, then placingk the foam rubber 49'on the sheet, then placing a second circular sheet of semi-cured rubber on the foam rubber, or felt, 49, then placing a ring of fabric 46 and a disc of fabric 48 in place and then subjecting the entire assembly to heat and pressure in a suitable mold to cure the rubber and bond the parts to each other.

The cushion means, or back-up cushion 51, formed by the soft, resilient cushion material 49 as disclosed in my said Patent 3,169,265 permits the polishing felt to exert uniform resilience and pressure throughout its operating life especially in the critical central area of the felt.

The anchoring means 54 of the invention includes laterally directed elements 55, in the plane of the side wall 41 of the anchoring portion 37, which extend into the recess means 40 for anchoring the felt to the block.r Preferably, the anchoring means 54 is a split ring 56 formed of two semi-circular sections 57 and 58, each defining an interior wall 59 or 60, which mate with, and seat against, the side wall 41. The interior walls 59 and 60 are of truncated conical configuration to conform with the undercut, tapered groove 42 so that the walls 59 and 60 of the sections 57 and 58 are `the laterally directed anchoring. elements of the embodiment illus-` trated.

Semi-circular ring section 58is permanently affixed to the peripheral portion 33 of the outer face 32 ofthe block 30 by suitable machine-screws 62. The truncated conical anchoring portion 37 of a new, or replacement felt 34 can thus be slid laterally into the section 58 to seat one half thereof. The othersemi-circular. section 57 is connected to block 30, by detachabley lmeans 63, preferably in the form of a plurality of lugs 64 or 65 each` fixed to the outside of the section 57' by machine screws 66 and fixed to the outside of the` block by machine `screws 67. Preferably also section 58 includes one or 1more laterally extending pins 68 mating `with corresponding laterally extending pin holes 69 in the other section y57 for aligning the interior walls 59 and 60 and for holding the parts firmly together. felt 34 has been seated in the semi-circular section ,58 the other semi-circular section is slid laterally into place and the screws 67 affixed to the block, thereby positively,` mechanically seating the thick felt'34 by means in front` of, and beyond, the plane of the outer face 32 .of block 30.

In FIGURE 3, a unitary felt 72 is shown which isl identical with the felt 34, except that the upstanding, truncated conical anchoring portion 73 is filled 4with felt The space 75 serves as a cushion means 76, sincethe central zone of theworking portion 77 is slightly compressible thereinto land the cylindrical felt` body` has` slight inherent resiliency.

Air is not trapped in the space 75 and the space, to-

gether with the axial opening 78 in the working portion 77, forms a passage for self feeding of polishing slurry through thefelt to the glass 31. In this embodiment, the

canvas @back-up disc 79 is annular and the inner side wall 80 and :bottom 81 of the space 75 is lined with the cured rubber covering layer 82.

In FIGURE 4, another embodiment is shown, in which the unitary composite felt 85,1is similar to felts 34 and 72 except that the cushioning and anchoring portion 86. is annular to define a space `87 with a closed bottom formed by the rubber layer 88. Upstanding'from, and

integral with, the rubber layer 88 are a pluralityy of resilient fiexible, spaced teeth 89 of rubber, or the like, for 1 providing cushion means 90 in the critical central zone of the felt. The workin-g portion 91 of felt 85 includes a plurality of slurry feed Atroughs such as 92, 93 and 94 1 for facilitating the feed of slurry to the glass 31; Suitable passages 95 connect the troughs to passage 78.

It will be apparent that other forms of detachable, split rings can be used to -retain the improved polishing felt of the invention on the face of the blockor that the- :block could be cast with a central cavity and laterally movable rods, lugs or pins be used to seat the upstanding anchoring portion of the felt. The anchoring means illustrated herein is preferred however, because it permits 1. In combination with arpolishing block having an outer, felt-supporting, face;

a unitary polishing felt of substantial thickness having p When a new, or replacement,`

face on said block, said means having laterally directed elements in the plane of said side wall extending into said recess means for anchoring said felt to said block, at least one said element being laterally detachable relative to said block.

2. A combination as specified in claim 1 wherein:

said polishin-g felt is of predetermined diameter, said inner anchoring portion is upstanding therefrom and of reduced diameter Iand said anchoring means is a split annular clamp and encircling the side wall of the inner anchoring portion of said iblock, said clamp including at least one clamp element secured to said outer face of said lblock and at least one clamp element laterally detachable from said block.-

3. A combination `as specified in claim 1 wherein:

said polishing felt is of predetermined diameter, said recess means is an undercut, annular groove in the side wall of the inner anchoring portion thereof and said anchoring means is a split annular clamp seated in said groove, said cla-mp comprising two semicircular elements, one permanently secured to the periphery of the -outer face of said block and the other laterally movable from said block.

4. A combination as specified in claim 1 wherein:

the side wall of said anchoring portion defines an inverted truncated cone of less diameter than said working portion;

said anchoring means is a split clamp fitting within said groove and peripherally affixed to the outer face of said block;

and said felt includes a layer of rubber covering the block and clamp engaging faces thereof, including the side wall of said groove.

5. A combination as specified in claim 1 wherein:

said polishing felt is of predetermined diameter, the

side wall of said anchoring portion defines an inverted, truncated cone of reduced diameter, said anchoring means is a split, annular clamp encircling said cone and said anchoring portion includes a reinforcing, covering enclosing a filler of resilient material for forming a centrally disposed cushion on said felt.

6. A polishing felt for use With a polishing block, said felt comprising:

a unitary cylindrical body of substantial thickness having a working portion with a polishing face of felt and an anchoring portion with a block-engaging face;

a side wall on said anchoring portion having laterally directed recess means extending inwardly toward the centre thereof;

and a liquid impermeable, reinforcing covering of sheet material adhered to said block engaging face and to said wall for sealing the same and strengthening said recess means.

7. A polishing felt as specified in claim 6 wherein:

said anchoring portion is an inverted, truncated cone of reduced diameter upstanding from, but integral with, said body.

8. A polishing felt as speciied in claim 6 wherein:

said anchoring portion is of less -diameter than the diameter of said body and comprises a filler of resilient, soft, cushion material enclosed in said liquid impermeable, reinforcing covering, said covering being adhered to said body.

9. A polishing felt `as specified in claim 6 wherein said anchoring portion is annular to form an inner side Wall and bottom and said covering is adhered to said inner side wall and bottom.

anchoring portion is annular to define a centrally dis posed space therein;

outer, felt-supporting face;

ROBERT C. RIORDON, Primary Examiner.

LEONARD S. SELMAN, Assistant Examiner.

10. A polishing felt las specified in claim 6 wherein sai l said felt includes cushion means within said space and` said working face includes a plurality of slurry feed troughs connected to said space.

11. A polishing felt as specified in claim 6 plus:

anchoring means adapted to be detachably mounted on said polishing block, said means having laterally directed elements in 4the plane of said side wall adapted to extend into said recess means for locking said felt thereto.

12. A polishing felt as specified in claim 11 wherein:

said anchoring portion is Yan inverted, truncated cone forming an undercut, tapered groove, and

said anchoring means is lan annular, split clamp detachably mounted in said -groove and detachably iixed to the periphery of the face of said block.

13. In combination with a polishing block having an a unitary polishing felt of substantial thickness and predetermined diameter, having an upstanding anchoring and cushioning portion of soft, resilient material, said portion being of reduced diameter proximate said felt supporting face;

an exterior side wall on said anchoring portion of inverted, truncated conical configuration forming an undercut annular groove, and

a split, annular clamp secured on the outer face of said block, said clamp having an interior side wall of truncated conical configuration seated against said exterior side wall for anchoring said felt to said block, and having a laterally slidable elemen-t detachable therefrom for removing said felt from said block.

14. A combination as specified in claim 13, wherein:

said upstandin-g anchoring portion is annular in contiguration to form a central space therein, and

resilient filler means in said central space for forming a back-up cushion in the critical central area of said felt.

15. A combination as specified in claim 13 plus:

a rubber-like, liquid impermeable layer fixed to said felt and covering said anchoring portion, inclu-ding said side Wall and recess means, for preventing slurry from reaching said block and said clamp.

16. A combination as specified in claim 13 wherein:

said clamp comprises two semi-circular sections, one said section being tixed to the outer face of said block, and the other said section constituting said laterally slidable element;

and detachable means afrixing the other said section to the outside of said iblock for permitting access thereto when said felt is in position on said block.

References Cited by the Examiner UNITED STATES PATENTS 743,308 11/ 1903 Messer 5 l-209 1,710,528 4/ 1929' lBeach 51-209 3,174,258 3/1965 Kenny 51-358 X 

1. IN COMBINATION WITH A POLISHING BLOCK HAVING AN OUTER, FLET-SUPPORTING, FACE; A UNITARY POLISHING FELT OF SUBSTANTIAL THICKNESS HAVING AN OUTER WORKING PORTION OF FELT, AN INNER ANCHORING AND CUSHIONING PORTION OF RESILIENT MATERIAL WITH A SIDE WALL AND A BLOCK-ENGAGING INNER FACE; SAID FELT HAVING LATERALLY DIRECTED RECESS MEANS EXTENDING INWARDLY FROM THE SIDE WALL OF SAID RESILIENT ANCHORING AND CUSHIONING PORTION TO RECEIVE ANCHORING ELEMENTS, AND ANCHORING MEANS SECURED ON THE OUTER, FELT SUPPORTING FACE ON SAID BLOCK, SAID MEANS HAVING LATERALLY DIRECTED ELEMENTS IN THE PLANE OF SAID SIDE WALL EXTENDING INTO SAID RECESS MEANS FOR ANCHORING SAID FELT TO SAID BLOCK, AT LEAST ONE SAID ELEMENT BEING LATERALLY DETACHABLE RELATIVE TO SAID BLOCK. 